Image display systems based on spatial light modulators (SLMs) are an alternative to image display systems that are based on cathode ray tubes (CRTs). SLM systems provide high resolution without the bulk of CRT systems.
Digital micro-mirror devices (DMDs) are one type of SLM, and may be used for either direct view or for projection displays. A DMD has an array of hundreds or thousands of tiny tilting mirrors, each of which represents one pixel. To permit the mirrors to tilt, each is attached to one or more hinges mounted on support posts, and spaced by means of an air gap over underlying control circuitry. The control circuitry provides electrostatic forces, which cause each mirror to selectively tilt. For display applications, image data is loaded to memory cells of the DMD and in accordance with this data, mirrors are tilted so as to either reflect light to, or deflect light from, the image plane.
One approach to providing color images in an SLM display system is to alternately address all pixels of a frame of the image with a different color. For example, each pixel might have a red, a green, and a blue value. Then, during each frame period, the pixels of that frame are addressed with their red, blue, then green data, alternatingly. A color wheel having three segments of these same colors is synchronized to the data so that as the data for each color is displayed by the SLM, the light incident on the SLM is filtered by the color wheel. For standard display rates of 60 images per second, the eye perceives the image as having the proper color.
To permit each pixel to be represented by values with more than one bit for each color, various modulation schemes can be used to vary the intensity of each color. For example, each pixel might have a 24-bit value, 8 bits for each color. This permits 2.sup.8 =256 levels of intensity for each color.